1. Field
The described technology relates generally to a fuel cell stack.
2. Description of the Related Art
A fuel cell stack includes a plurality of membrane electrode assemblies (MEAs) and a separator (referred to as ‘bipolar plate’) that is positioned between the MEAs.
Here, each MEA includes an electrolyte membrane, an anode that is positioned at one side of the electrolyte membrane, and a cathode that is positioned at the other side of the electrolyte membrane. The separator forms a fuel channel at one surface toward the anode to supply fuel to the anode and forms an oxidizing agent channel at one surface toward the cathode to supply an oxidizing agent to the cathode. Accordingly, electrical energy is generated by a hydrogen oxidation reaction of the anode and an oxygen reduction reaction of the cathode, and a heat and water are additionally generated.
Here, the electrolyte membrane has an ion exchange function of moving protons that are generated in the anode to the cathode. Phosphoric acid (H3PO4) is used as a conductive material for exchanging ions in an electrolyte membrane that is used for an MEA for a high temperature. The MEA for a high temperature is generally manufactured by impregnating a polybenzimidazole (PBI) membrane with phosphoric acid (H3PO4). In this case, in order to embody optimum performance of the MEA for a high temperature, it is known that an impregnation ratio of phosphoric acid is about 300% (a weight ratio of an electrolyte membrane and phosphoric acid). Therefore, when phosphoric acid (H3PO4) having a weight of about three times or more than the electrolyte membrane is impregnated, mechanical strength of the electrolyte membrane is lowered, and thus when the MEA is manufactured, the electrolyte membrane may be damaged.
Further, when a fuel cell is operated for a long time, phosphoric acid of the electrolyte membrane can leak to the outside by water that is generated in the cathode and thus performance of the fuel cell can be deteriorated.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.